Polishing slurries for copper and associated materials

ABSTRACT

A chemical mechanical polishing slurry and method for using the slurry for polishing copper, barrier material and dielectric material that comprises a first and second slurry. The first slurry has a high removal rate on copper and a low removal rate on barrier material. The second slurry has a high removal rate on barrier material and a low removal rate on copper and dielectric material. The first and second slurries at least comprise silica particles, an oxidizing agent, a corrosion inhibitor, and a cleaning agent.

This is a continuation in part of U.S. patent application Ser. No.09/562,298 filed May 1, 2000, U.S. Pat. No. 6,409,787 in the names ofThomas H. Baum, Long Hoanghuan, Cary Regulski, and William Alan, for“Polishing Slurries for Copper and Associated Materials.”

BACKGROUND OF THE INVENTION

The present invention relates to a chemical mechanical polishing slurryfor surfaces of a semiconductor wafer, and more particularly, to achemical mechanical polishing slurry and a method for using the slurryto remove and polish copper, barrier materials and dielectric materialslayered on semiconductor wafer surfaces.

Semiconductor wafers are used to form integrated circuits. Thesemiconductor wafer typically includes a substrate, such as silicon,upon which dielectric materials, barrier materials, and metal conductorsand interconnects are layered. These different materials haveinsulating, conductive or semi-conductive properties. Integratedcircuits are formed by patterning regions into the substrate anddepositing thereon multiple layers of dielectric material, barriermaterial, and metals.

In order to obtain the correct patterning, excess material used to formthe layers on the substrate must be removed. Further, to obtainefficient circuits, it is important to have a flat or planarsemiconductor wafer surface. Thus, it is necessary to polish certainsurfaces of a semiconductor wafer.

Chemical Mechanical Polishing or Planarization (“CMP”) is a process inwhich material is removed from a surface of a semiconductor wafer, andthe surface is polished (planarized) by coupling a physical process suchas abrasion with a chemical process such as oxidation or chelation. Inits most rudimentary form, CMP involves applying slurry, a solution ofan abrasive and an active chemistry, to a polishing pad that buffs thesurface of a semiconductor wafer to achieve the removal, planarization,and polishing process. It is not desirable for the removal or polishingprocess to be comprised of purely physical or purely chemical action,but rather the synergistic combination of both in order to achieve fastuniform removal. In the fabrication of integrated circuits, the CMPslurry should also be able to preferentially remove films that comprisecomplex layers of metals and other materials so that highly planarsurfaces can be produced for subsequent photolithography, or patterning,etching and thin-film processing.

Recently, copper has been used as the metal interconnect forsemiconductor wafers. Typically for copper technology, the layers thatare removed and polished consist of a copper layer (about 1-1.5 μmthick) on top of a thin copper seed layer (about 0.05-0.15 μm thick).These copper layers are separated from the dielectric material surfaceby a layer of barrier material (about 50-300 Å thick). The key toobtaining good uniformity across the wafer surface after polishing is byusing a slurry that has the correct removal selectivities for eachmaterial. If appropriate material removal selectivity is not maintained,unwanted dishing of copper and/or erosion of the dielectric material mayoccur.

Dishing occurs when too much copper is removed such that the coppersurface is recessed relative to the dielectric surface of thesemiconductor wafer. Dishing primarily occurs when the copper andbarrier material removal rates are disparate. Oxide erosion occurs whentoo much dielectric material is removed and channels are formed in thedielectric material on the surface of the semiconductor wafer relativeto the surrounding regions. Oxide erosion occurs when the dielectricmaterial removal rate is locally much higher than the copper removalrate. Dishing and oxide erosion are area dependent being wafer patternand pitch dependent as well.

Typical commercial CMP slurries used to remove overfill material andpolish semiconductor wafer surfaces have a barrier material removal ratebelow 500 Å/min. Further, these slurries have a copper to barriermaterial removal rate selectivity of greater than 4:1. This disparity inremoval rates during the removal and polishing of the barrier materialresults in significant dishing of copper on the surface of thesemiconductor wafer and/or poor removal of the barrier material.

Another problem with conventional CMP slurries is that the removalchemistry of the slurry is compositionally unstable. Further, many ofthe colloidal abrasives agglomerate after relatively short time framesfollowing addition to the supporting chemistry. Both of these problemslead to significant operational obstacles.

A further problem in commercial CMP slurries is that the abrasivematerials in the slurries produce defects in the form of microscratches. These slurries also have poor planarization efficiency, whichis the ability of the slurry to polish high points preferentially overlow points on the surface of the wafer. Micro scratches and poorplanarization efficiency result in integrated circuits with increaseddefects and a lower yield.

Still another problem of commercial CMP slurries is that the chemicalsthat make up the slurries produce a copper surface that has a highcorrosion tendency post polish.

An object of this invention, therefore, is a CMP slurry that employs atwo-step slurry approach. The slurry used in the first step has a highcopper removal rate and a comparatively low barrier material removalrate. The slurry used in the second step has a relatively high barriermaterial removal rate, comparable removal rate for copper and lowremoval rate on the dielectric material. By using this two-step slurryapproach, the first and second slurries can provide the appropriateselectivity ranges to minimize copper dishing and oxide erosion, therebyproviding a viable CMP approach to advanced device manufacturing.

Another object of the invention is for the first and second slurries tohave stable removal chemistry.

Yet another object is to use abrasives in the first slurry that achievehigh copper removal rates, but minimal barrier material removal rates,and to use abrasives in the second slurry that provide superior removalrates on barrier material and low removal rates for copper, which alsominimize micro scratch defects and provide very good planarizationefficiency.

It is a further object of this invention to employ active coppercleaning chemistry and corrosion inhibitors in the slurry to minimizecopper corrosion post polish, and to eliminate post-polish cleaningsteps.

These and other objects and advantages of the invention will be apparentto those skilled in the art upon reading the following detaileddescription and upon reference to the drawings.

SUMMARY OF THE INVENTION

The present invention is directed to a chemical mechanical polishingslurry comprising a first slurry, which has a high removal rate oncopper and a low removal rate on barrier material and a second slurry,which has a high removal rate on barrier material and a low tocomparable removal rate on copper and the associated dielectricmaterial. The first and second slurries comprise silica particles, anoxidizing agent, a corrosion inhibitor, and a cleaning agent. Alsodisclosed as the present invention is a method for chemical mechanicalpolishing copper, barrier material and dielectric material with thepolishing slurry of the present invention. As will become apparent fromthe discussion that follows, the stable slurry and method of using theslurry provide for removal of material and polishing of semiconductorwafer surfaces with significantly no dishing or oxide erosion, withsignificantly no surface defects and good planarization efficiency, andproduce a copper surface with minimal corrosion tendency post-polish.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a semiconductor wafer prior tochemical mechanical polishing.

FIG. 2 is a cross sectional view of the semiconductor wafer of FIG. 1following chemical mechanical polishing with the first slurry, accordingto the present invention.

FIG. 3 is a cross sectional view of the semiconductor wafer of FIG. 2following chemical mechanical polishing with the second slurry,according to the present invention.

FIG. 4 is a cross sectional view of a semiconductor wafer illustratingcopper dishing.

FIG. 5 is a cross sectional view of a semiconductor wafer illustratingoxide erosion.

FIG. 6 is a transmission electron micrograph (TEM) showing 13 nm silicaparticles of the present invention.

FIG. 7 is the size distribution of 13 nm silica particles of the presentinvention determined with Coulter N4 Plus particle analyzer.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a semiconductor wafer 10 prior to CMP. As shown,substrate 11 may be made of any conventional semiconductor materials,including silicon or germanium or silicon-germanium. Layered on top ofthe substrate 11 is dielectric material 12, which is preferentiallysilicon oxide, low k dielectrics comprised substantially of siliconoxide or a carbon containing silicon oxide. The instant invention is notlimited to such dielectric materials and is also useful for removal ofdielectrics such as fluoride doped silicon glass (FSG). Layered on thedielectric material 12, is barrier material 13. The barrier materiallayer 13 is typically about 50 to 300 Å thick. The barrier material 13may be any material conventionally used, but is typically chosen fromthe group of tungsten nitride, tantalum, tantalum nitride, titaniumnitride, silicon doped tantalum nitride or silicon doped titaniumnitride. Finally, a layer of copper 14 covers the barrier material layer13, and extends into trenches 14 a, 14 b, and 14 c. The copper layer 14is usually about 0.1-0.15 μm thick and the copper layer 14 in FIG. 1includes a thin copper seed layer, which is usually about 0.05-0.15 μmthick.

The invention is a CMP slurry designed to polish copper 14 andassociated barrier materials 13 such as tungsten nitride, tantalum,tantalum nitride, silicon doped tantalum nitride, titanium nitride andsilicon doped titanium nitride. The chemical mechanical polishing slurryof the present invention is comprised of two parts. The first slurry isa copper selective slurry used to remove the bulk copper down to thebarrier layer (FIG. 2). The first slurry has a high removal rate ofcopper and a low removal rate of barrier material. The second slurry isselective to the barrier layer and removes the barrier material down tothe dielectric material. The barrier and copper rate are comparable orthe barrier removal is greater than copper for this step (FIG. 3). Thevarious removal rates of the first and second slurries on variousmaterials are shown in Table 1. In this way, two slurries togethercomprise a combined package to polish copper metallization schemes forintegrated circuit manufacturing.

TABLE 1 Removal Rates of the First and Second Slurries on DifferentMaterials* Selectivity First Slurry Second Slurry Material: Cu RemovalRates Removal Rates First Second LAYER (Å/min) (Å/min) Slurry SlurryCopper >5000 <1000 Tantalum <500 >1000 1:10 1:1 Tantalum <500 >1000 1:101:1 Nitride Thermal Oxide <150 <150 1:50 1:6 *(Down Force = 5 psi, FlowRate = 200 mL/min, Table Speed = 90 rpm, Quill Speed = 50 rpm, Pad Type= IC 1000)

In one embodiment, the first step slurry removes copper material at ahigher rate than barrier material. Preferably the copper materialremoval rate is greater than 3000 Å/min, more preferably greater than4000 Å/min and most preferably greater than 5000 Å/min; and the barriermaterial removal rate is less than 600 Å/min and more preferably lessthan 50 Å/min. The second step slurry removes barrier material at a rateof at least 500 Å/min, more preferably at least 750 Å/min and mostpreferably at least 1000 Å/min, having a barrier material to dielectricmaterial selectivity of from about 5:1, more preferably from about 7:1and most preferably from about 15:1.

Referring to FIG. 1, the present invention includes a method forchemical mechanical polishing copper 14, barrier material 13 anddielectric material 12, comprises the following steps: (1) providing afirst chemical mechanical polishing slurry that has a high removal rateon copper 14 and a low removal rate on barrier material 13; (2) chemicalmechanical polishing a semiconductor wafer surface 10 with the firstslurry; (3) providing a second chemical mechanical polishing slurry thathas a high removal rate on barrier material 13 a comparable removal rateon copper 14 and a low removal rate on the dielectric material 12; and(4) chemical mechanical polishing the semiconductor wafer surface 10with the second slurry.

Generally, the slurry is applied to a pad contained on a polishinginstrument. Polishing instrument parameters such as down force (DF),flow rate (FR), table speed (TS), quill speed (QS), and pad type can beadjusted to effect the results of the CMP slurry. These parameters areimportant in obtaining efficient planarization results and limitingdishing and erosion. Although these parameters may be altered, when usedwith the CMP slurry of the present invention, the standard conditionsused are DF of 5psi, FR of 200 mL/min, TS of 90 rpm, QS of 50 rpm, andthe IC 1000 pad type.

FIG. 2 illustrates the semiconductor wafer 10 of FIG. 1, after steps (1)and (2) of the present method for CMP have been carried out, and thesemiconductor wafer surface has been polished with the first slurry.When FIG. 2 is compared to FIG. 1, the top copper layer 14 in FIG. 1 hasbeen preferentially removed, and only the copper in the trenches (FIG.2) 18 a, 18 b, and 18 c is left. As shown in FIG. 2 the barrier materiallayer 17 is substantially in tact, and the dielectric material 16 basedon substrate 15 is still unexposed.

Similarly, FIG. 3 illustrates the semiconductor wafer 10 of FIGS. 1 and2, after steps (3) and (4) of the present method for CMP have beencarried out, and the semiconductor wafer surface has been polished withthe second slurry. As shown in FIG. 3, the barrier material layer 21 hasbeen removed down to the dielectric material 20. The second slurry alsoremoved just enough of the copper in trenches 22 a, 22 b, and 22 c sothat the surface of the semiconductor wafer 10 is flat and planar. Thesecond slurry also serves to polish the newly exposed surface, includingthe dielectric material 20, the barrier material 21 a, 21 b, 21 c, andthe copper 22 a, 22 b, 22 c. All of these materials are based onsubstrate 19.

By using the first and second slurries of the claimed invention, withthe selectivities described in Table 1, and following the describedmethod, copper dishing (FIG. 4) and oxide erosion (FIG. 5) can beminimized. FIG. 4 shows a semiconductor wafer to which a CMP slurry hasbeen applied, which had a higher selectivity for copper 26 a, 26 b, 26 cthan for the barrier material 25 a, 25 b, 25 c or dielectric material24. As a result, disparate amounts of copper are removed from thesurface of the semiconductor wafer. This is known as copper dishing andis shown by the dish-like troughs 27 a, 27 b, and 27 c in the trenchesof copper 26 a, 26 b, 26 c. The CMP slurry of the present invention andmethod of using this slurry greatly reduces copper dishing.

Similarly, FIG. 5 shows a semiconductor wafer to which a CMP slurry hasbeen applied, which has a higher selectivity for the dielectric material29 than for the barrier material 30 a, 30 b, 30 c, or copper 31 a, 31 b,31 c. As a result, disparate amounts of dielectric material are removedfrom the surface of the semiconductor wafer. This is known as oxideerosion and is shown by the indentions and/or reduction of thedielectric material 29 a, 29 b. The CMP slurry of the present inventionand method of using this slurry greatly reduces oxide erosion.

Turning now to the composition of the CMP slurry, generally the firstand second slurries comprise silica particles, an oxidizing agent, acorrosion inhibitor, and a cleaning agent. Preferably, the CMPcompositions comprise a first slurry comprising from about:

weight % 1-10% fumed or colloidal silica particles 1-12% oxidizingagent; 0-2% corrosion inhibitor;

and a second slurry comprising from about:

weight % 1-10% fumed or colloidal silica particles; 0.1-1.0% oxidizingagent; and 0-2% corrosion inhibitor.

The chemistry of the first and second slurries should be stable and havea pH in the range of about 2 to 5. The first and second slurries maycontain potassium or ammonium hydroxide in such amounts to adjust the pHto a range of about 2 to 5.

The preferred oxidizing agent for the first and second slurries ispotassium iodate formed by reaction of HIO₃ with KOH. The corrosioninhibitor and cleaning agent for the first and second slurries should bea carboxylic acid. More specifically, the carboxylic acid may be chosenfrom the group of glycine, oxalic acid, malonic acid, succinic acid andnitrilotriacetic acid. Alternatively, the carboxylic acid may be adicarboxylic acid that preferentially has a nitrogen containingfunctional group. In the most preferred form, the corrosion inhibitorand cleaning agent for the first and second slurries is iminodiaceticacid. Inorganic acids such as phosphoric, nitric and hydrochloric wereadded to adjust pH and accelerate copper removal rates.

The use of potassium iodate as the oxidizing agent and carboxylic acidsas the corrosion inhibitors and cleaning agents and inorganic acids asaccelerating agents creates a stable removal chemistry in the pH regionof about 2 to 5, for the first and second slurries. Further, the use ofcopper corrosion inhibitors and cleaning agents minimizes coppercorrosion, as indicated by low static etch rates of roughly less than 50Å/min on copper.

The silica particles of the first and second slurries can beprecipitated. The precipitated particles usually range from about 3 to100 nm in size and can be spherical. An alternative to precipitatedsilica particles in the first slurry is fumed silica. Generally, thefumed silica has a mean particle size of less than 700 nm.

Alternatively, and more preferred is to use colloidal silica particlesof the type described. The colloidal silica particles can range fromabout 3 to 100 nm in size, and can be spherical. Preferentially, whenthe first and second slurries employ spherical colloidal particles, theparticles should have a narrow size distribution. More specifically,about 99.9% of the spherical colloidal particles should be within about3 sigma of a mean particle size with negligible particles larger thanabout 500 nm.

The first slurry, thus, can employ either precipitated spherical silicaparticles in the size range of 3 to 100 nm, or fumed silica with meanparticle size less than about 700 nm. These particles coupled with theiodate chemistry allows the first slurry to achieve high copper removalrate but minimal barrier material removal rate. Colloidal silica, with anarrow size distribution, minimizes micro scratch defects and providessuperior removal rates on barrier materials, greater than about 1000Å/min, and low removal rates for copper for the second slurry. Further,spherical silica abrasives with a mean size of less than about 100 nmprovide very good planarization efficiency.

The pH, oxidizing agents, modifying agents, abrasive particlecomposition and size distribution, and weight percent were evaluated toestablish a baseline for removal rates and selectivity.

EXAMPLE 1

Precipitated silica mean particle sizes of 8 nm, 20 nm, and 70 nm weretested. The fumed silica particle size tested was less than 700 nm. Theoptimum CMP slurry, including the first and second slurry, had aprecipitated silica mean size of less than about 100 nm. The optimumfumed silica abrasive mean size for the first slurry is less than about700 nm. The optimum CMP slurry formulations contain 1-10% precipitatedsilica, or fumed silica for the first slurry.

Further, different types of abrasive particles were studied to maximizethe removal and selectivity characteristic of the slurry. Precipitatedsilica abrasives, with mean size distributions of 4 nm, 8 nm, 13 nm, 20nm and 70 nm were tested. FIG. 6 shows a TEM picture of 13 nm slurry.The size distribution of these particles is presented in FIG. 7. Fumedsilica, with a mean particle size of less than about 700 nm, was alsoevaluated. All of these mean size distributions can be used to achieveeffective polishing rates and selectivities for the first and secondslurries.

EXAMPLE 2

Different pH ranges were tested for the first and second slurries (SeeTable 2 and 3). The precipitated silica abrasives had a starting pHrange of 9-11 and the fumed silica had a starting pH range of 2-7. Theoptimum CMP slurry was found to be acidic. Thus, the pH ranges werealtered to the 2 to 5 range by adding potassium, sodium or ammoniumhydroxide in appropriate amounts to solutions of iodic acid, cleaningagent and corrosion inhibitor.

EXAMPLE 3

Several formulations of the first slurries were prepared. Thecharacteristics of these formulations are described in Table 2. Thefirst slurry is optimally comprised of formula 5, for colloidal silicaparticles, and formula 19 for fumed silica particles. Thus, the firstslurry is preferentially comprised of 1-10% colloidal silica withparticle size 3 to 100 nm, or 1-5% fumed silica with mean particle sizeof less than about 700 nm. Further, the active chemistry for the optimumfirst slurry is about 1-12% potassium iodate (KIO₃, formed by reactionof HIO₃ with KOH), which is used as the oxidizing agent for the copper,about 0-5% concentrated inorganic acid as a copper activating agent, and0-2% iminodiacetic acid (IDA) as the copper corrosion inhibitor andcleaning agent.

TABLE 2 Formulations for the First Slurry Copper Copper Thermal TantalumOxidizer, Inhibitor, Activator, Neutralizer, Abrasive, Oxide CopperTantalum Nitride Formula % % % % % pH RR* RR* RR RR  1 HIO₃, IDA, H₃PO₄KOH Colloidal 2.4 — 3176 — — 8.22 1.5 1.764 4.523; (13 nm), NH4OH,3.7768  2 HIO₃, IDA, H₃PO₄ KOH, Colloidal 2.7 113 4713 — — 12.33 1.5 0.55.022 (13 nm)k 1  3 HIO₃, IDA, — NH4OH, Colloidal 3.0 126 4800 — — 101.5 2.685 (13 nm), 1  4 HIO₃, IDA, — KOH, Colloidal 2.8 126 5165 — — 101.5 4.084 (13 nm), 1  5! HIO₃, IDA, H₃PO₄, KOH, Colloidal 2.9 151 6530453 590 10 1.5 0.5 4.523 (13 nm), 1  6 HIO₃, IDA, H₃PO₄, KOH, Colloidal3.1 115 6877 422 528 12.33 1.5 0.5 5.486 (13 nm), 1  7 HIO₃, IDA, H₃PO₄,KOH, Colloidal 3.1 115 6877 422 528 12.33 1.5 0.5 5.486 (13 nm), 1  8HIO₃, IDA, H₃PO₄, KOH, Colloidal 3.1 112 4797 494 730 8.22 1.5 0.5 3.978(13 nm), 1  9 HIO₃, — HCl, KOH, Colloidal 6.0 117 423 878 1031 8.22 0.15g 4.284 (13 nm), 1 10 HIO₃, IDA, H₃PO₄, KOH, Colloidal 3.4 134 2138 550618 4.11 1.5 0.5 2.92 (13 nm), 1 11 HIO₃, IDA, H₃PO₄, KOH, Colloidal 3.6105 2134 512 882 4.11 1.5 0.5 2.92 (13 nm), 1 12 HIO₃, IDA, H₃PO₄, KOH,Colloidal 6.0 106 1448 890 1047 6.17 1.5 0.5 4.087 (13 nm), 13 HIO₃,IDA, H₃PO₄, KOH, Colloidal 3.5 140 3900 720 1066 4.11 1.5 0.5 2.918 (13nm), 1 14 HIO₃, IDA, H₃PO₄, KOH, Colloidal 3.6 45 4157 527 623 4.11 1.50.5 3.012 (8 nm), 1 15 HIO₃, IDA, H₃PO₄, KOH, Colloidal 3.7 172 6852 649842 4.11 1.5 0.5 3.067 (20 nm), 1 16 HIO₃, IDA, H₃PO₄, KOH, Colloidal3.6 171 2720 451 625 4.11 1.5 0.5 3.13 (70 nm), 1 17 HIO₃, IDA, H₃PO₄,KOH, Colloidal 3.6 118 3973 832 1028 4.11 1.5 0.5 2.918 (13 nm), 1 18HIO₃, IDA, — KOH, Colloidal 3.5 167 5630 728 946 4.11 1.5 2.474 (13 nm),1 19! HIO₃, IDA, H₃PO₄, KOH, fumed, 1 3.6 15 4823 2.4 −10 4.11 1.5 0.52.918 *“RR” means removal rates in Å/min. Stock Solutions: HIO₃ (50% byweight); H₃PO₄ (85.87% by weight); KOH (45-46% by weight); NH₄OH (28-30%by weight); HNO₃ (68-70% by weight); HCl (36-38% by weight)

As can be seen from Table 2, all of the first slurry formulations of thepresent invention were effective in achieving acceptable copper removalrates, and semiconductor wafer surfaces of high quality. Thus, the firstslurry is preferentially comprised of 1-10% colloidal silica withparticle size of less than about 100 nm.

EXAMPLE 4

Several formulations of the second slurry were prepared. Thecharacteristics of these formulations are described in Table 3. Thesecond step slurry is dependent on the copper removal rate requirementand therefore is optimally comprised of either formula 6 or 9. Theactive chemistry for the optimum second slurry is 0.1-1% potassiumiodate (KIO₃, formed by reaction of HIO₃ with KOH) as the oxidizingagent for the copper, 0-5% concentrated inorganic acid and 0-2%iminodiacetic acid as the copper corrosion inhibitor and cleaning agent.Table 3. Formulations for the Second Slurry

Copper Copper Thermal Tantalum Oxidizer, Inhibitor, Activator,Neutralizer, Abrasive, Oxide Copper Tantalum Nitride Formula % % % % %pH RR* RR* RR RR  1 HIO₃, IDA, — KOH Colloidal 3.4 101 430 462 2128 0.11.5 1.005 (13 nm), 1  2 HIO₃, IDA, HNO₃, KOH Colloidal 3.0 100 572 1461749 0.1 1.5 10 13.66 (13 nm), 1  3 HIO₃, IDA, HNO₃, 5; KOH Colloidal3.0 53 358 50.21 751 0.1 0.1 HCl, 5 13.14 (13 nm), 1  4 HIO₃, IDA,H₃PO₄, KOH Colloidal 2.7 116 574 772 1471 0.1 1.5 1.5 2.079 (13 nm), 1 5 HIO₃, IDA, HNO₃, KOH Colloidal 3.1 149 511 670 2087 0.1 1.5 2 3.674(13 nm), 1  6! HIO₃, IDA, HNO₃, NH4OH, Colloidal 3.1 130 239 623 21460.1 1.5 2.31 2.507 (13 nm), 1  7 HIO₃, IDA, — KOH, Colloidal 3.4 1261053 657 1200 0.1 1.5 1.312 (13 nm), 1  8 HIO₃, IDA, — KOH, Colloidal3.5 200 0 >3000 217 0 2 1.305 (13 nm), 1  9 HIO₃, IDA, — KOH, Colloidal3.5 120 1120 731 907 0.5 1.5 1.086 (13 nm), 1 10 HIO₃, IDA, — KOH,Colloidal 3.5 131 1208 901 856 1.5 1.5 1.443 (13 nm), 1 *“RR” meansremoval rates in Å/min. Stock Solutions: HIO₃ (50% by weight); H₃PO₄(85.87% by weight); KOH (45-46% by weight); NH₄OH (28-30% by weight);HNO₃ (68-70% by weight); HCl (36-38% by weight)

As can be seen from Table 3, all of the second slurry formulations ofthe present invention were effective in achieving acceptable barrierdielectric and copper removal rates, and semiconductor wafer surfaces ofhigh quality.

The first and second slurries described herein, may also be used in amethod of chemical mechanical polishing as described above. Also, whilethis invention has been disclosed and discussed primarily in terms ofspecific embodiments thereof, it is not intended to be limited thereto.Other modifications and embodiments will be apparent to the worker inthe art.

What is claimed is:
 1. A method for chemical mechanical polishingcopper, barrier material and dielectric material, the method whichcomprises the steps of: providing a first chemical mechanical polishingslurry having a removal rate on copper that is at least 3000 Å/min;chemical mechanical polishing a semiconductor wafer surface with saidfirst slurry; providing a second chemical mechanical polishing slurryhaving, a pH in a range of from about 2 to 5, and a removal rate on saidbarrier material that is greater than 500 Å/min, a removal rate on saidcopper that is less than or equal to the removal rate of said barriermaterial and a removal rate on said dielectric material that is lessthan the removal rate of said barrier material; and chemical mechanicalpolishing said semiconductor wafer surface with said second slurry. 2.The method of claim 1 wherein said first slurry has a copper removalrate of greater than 5000 Å/min and a barrier material removal rate ofless than 500 Å/min.
 3. The method of claim 1 wherein said first slurrycomprises about 1-10% fumed or colloidal silica, 1-12% oxidizing agent;and 0-2% corrosion inhibitor.
 4. The method of claim 1 wherein saidfirst slurry comprises from about 1-10% colloidal silica, about 1-12%potassium iodate, about 0-5% concentrated inorganic acid, and about 0-2%iminodiacetic acid.
 5. The method of claim 1 wherein said first slurrycomprises about 1-5% fumed silica, about 1-12% potassium iodate, about0-5% concentrated inorganic acid, and about 0-2% iminodiacetic acid. 6.The method of claim 3 wherein said colloidal silica has a particle sizeof about 3 to 100 nm.
 7. The method of claim 3 wherein said fumed silicahas a mean particle size of less than about 700 nm.
 8. The method ofclaim 3 wherein said first slurry has a pH in a region of about 2 to 5.9. The method of claim 4 wherein said first slurry has a pH in a regionof about 2 to
 5. 10. The method of claim 1 wherein said second slurryhas a barrier material removal rate of greater than 1000 Å/min and acopper removal rate of less than 1000 Å/min and dielectric materialremoval rate of less than 500 Å/min.
 11. The method of claim 1 whereinsaid second slurry comprises about 1-10% colloidal or fumed silica,0.1-1.0% oxidizing agent; and 0-2% corrosion inhibitor.
 12. The methodof claim 1 wherein said second slurry comprises about 1-10% colloidal,about 0.1-1% potassium iodate, 0-5% concentrated inorganic acid andabout 0-2% iminodiacetic acid.
 13. The method of claim 12 wherein saidcolloidal silica has a particle size of less than about 100 nm.
 14. Themethod of claim 12 wherein said first slurry has a copper removal rateof greater than 5000 Å/min and a barrier material removal rate of lessthan 500 Å/min and said second slurry has a barrier material removalrate of greater than 1000 Å/min and a copper removal rate of less than1000 Å/min and a dielectric material removal rate of less than 500 Å/mi.15. The method of claim 13 wherein said first slurry has a copperremoval rate of greater than 5000 Å/min and a barrier material removalrate of less than 500 Å/min and said second slurry has a barriermaterial removal rate of greater than 1000 Å/min and a copper removalrate of less than 1000 Å/min and a dielectric material removal rate ofless than 500 Å/min.
 16. A slurry for chemical mechanical polishingcopper, barrier material and dielectric material, comprising: a firstslurry, having a removal rate on copper that is at least 3000 Å/min; anda second slurry, having a pH in a range of from about 2 to 5 and aremoval rate on said barrier material that is greater than 500 Å/min, aremoval rate on copper that is less than or equal to the removal rate ofsaid barrier material and a removal rate on said dielectric materialthat is less than the removal rate of said barrier material.
 17. Thechemical mechanical polishing slurry of claim 16, wherein said firstslurry comprises: from about 1-10 weight % fumed or colloidal silicaparticles from about 1-12 weight % oxidizing agent; from about 0-2weight % corrosion inhibitor;

and said second slurry comprises: from about 1-10 weight % fumed orcolloidal silica particles; from about 0.1-1.0 weight % oxidizing agent;and from about 0-2 weight % corrosion inhibitor.


18. The chemical mechanical polishing slurry of claim 16, wherein saidfirst slurry has a copper removal rate of greater than 5000 Å/min and abarrier material removal rate of less than 500 Å/min.
 19. The chemicalmechanical polishing slurry of claim 16, wherein said second slurry hasa barrier material removal rate of greater than 1000 Å/min and a copperremoval rate of less than 1000 Å/min and dielectric material removalrate of less than 500 Å/min.
 20. The chemical mechanical polishingslurry of claim 16, wherein said dielectric material is silicon oxide.21. The chemical mechanical polishing slurry of claim 16, wherein saidbarrier material is selected from the group consisting of: tungstennitride, tantalum, tantalum nitride, silicon doped tantalum nitride,titanium nitride and silicon doped titanium nitride.
 22. The chemicalmechanical polishing slurry of claim 16, wherein said barrier materialis tantalum.
 23. The chemical mechanical polishing slurry of claim 16,wherein said barrier material is tantalum nitride or silicon dopedtantalum nitride.
 24. The chemical mechanical polishing slurry of claim22, wherein said first slurry has a copper removal rate of greater than5000 Å/min and a tantalum removal rate of less than 500 Å/min, and saidsecond slurry has a tantalum removal rate of greater than 1000 Å/min anda copper removal rate of less than 1000 Å/min and a dielectric materialremoval rate less than 500 Å/min.
 25. The chemical mechanical polishingslurry of claim 16, wherein said first and second slurries are stableand have a pH region of about 2 to
 5. 26. The chemical mechanicalpolishing slurry of claim 16 wherein said first slurry comprises about1-10% colloidal silica, about 1-12% potassium iodate, about 0-5%concentrated inorganic acid, and about 0-2% iminodiacetic acid.
 27. Thechemical mechanical polishing slurry of claim 16 wherein said firstslurry comprises about 1-5% fumed silica, about 1-12% potassium iodate,about 0-5% concentrated inorganic acid, and about 0-2% iminodiaceticacid.
 28. The chemical mechanical polishing slurry of claim 26 whereinsaid colloidal silica has a particle size of about 3 to 100 nm.
 29. Thechemical mechanical polishing slurry of claim 27 wherein said fumedsilica has a mean particle size of less than 700 nm.
 30. The chemicalmechanical polishing slurry of claim 26, wherein said first slurry isstable and has a pH in a range of about 2 to
 5. 31. The chemicalmechanical polishing slurry of claim 27, wherein said first slurry isstable and has a pH in a range of about 2 to
 5. 32. The chemicalmechanical polishing slurry of claim 16, wherein said second slurrycomprises about 1-10% colloidal silica, about 0.1-1% potassium iodate,and about 0-2% iminodiacetic acid and 0-5% concentrated inorganic acid.33. The chemical mechanical polishing slurry of claim 32, wherein saidcolloidal silica has a particle size of less than 100 nm.
 34. Thechemical mechanical polishing slurry of claim 32 wherein said secondslurry is stable.
 35. The method of claim 8, wherein said first andsecond slurries further comprise a pH modifier selected from the groupconsisting of potassium or ammonium hydroxide.
 36. The method of claim9, wherein said first and second slurries further comprise a pH modifierselected from the group consisting of potassium or ammonium hydroxide.37. The chemical mechanical polishing slurry of claim 16, wherein saidfirst and second slurries further comprise a pH modifier selected fromthe group consisting of potassium or ammonium hydroxide.
 38. Thechemical mechanical polishing slurry of claim 30, wherein said first andsecond slurries further comprise a pH modifier selected from the groupconsisting of potassium or ammonium hydroxide.
 39. The chemicalmechanical polishing slurry of claim 31, wherein said first and secondslurries further comprise a pH modifier selected from the groupconsisting of potassium or ammonium hydroxide.
 40. The chemicalmechanical polishing slurry of claim 32, wherein said first and secondslurries further comprise a pH modifier selected from the groupconsisting of potassium or ammonium hydroxide.